1. Field of the Invention
The present invention relates to a method and apparatus for facilitating recovery from dysphagia.
2. Description of the Related Art
Dysphagia is the condition whereby a patient has difficulty in swallowing, or is unable to swallow. Dysphagia may be caused, for example, by stroke, neurodegenerative diseases, brain tumours or in some case by other co-morbidity such as respiratory disorders.
Swallowing is a rigidly ordered sequence of events that results in the propulsion of food from the mouth through the pharynx and esophagus to the stomach. At the same time, respiration is inhibited and food is prevented from entering into the trachea. Swallowing can be initiated voluntarily, but thereafter it is almost entirely under reflex control. The swallowing reflex is typically initiated by sensory impulses from tactile receptors (particularly those located near the opening of the pharynx) being transmitted to certain areas in the medulla. The central integrating areas for swallowing lie in the medulla and lower pons; they are collectively called the swallowing centre. Motor impulses travel from the swallowing centre to the musculature of the pharynx and upper esophagus via various cranial nerves. This lower swallowing centre in the brainstem is under regulatory control by higher centres in the cerebral cortex. These higher swallowing centres or regions control the voluntary initiation and modulation of the swallow.
Swallowing occurs in three stages. In the oral or voluntary phase, food is moved towards the back of the mouth by the tongue, and forced into the pharynx, where it stimulates the tactile receptors that initiate the swallowing reflex.
In the pharyngeal stage of swallowing, food passes through the pharynx by constriction of the walls of the pharynx, backward bending of the epiglottis, and an upward and forward movement of the larynx and trachea. During the pharyngeal stage, respiration is reflexively inhibited.
In the esophageal stage of swallowing, food moves down the esophagus and into the stomach, assisted by one or more peristaltic waves.
Although the main function of swallowing is the propulsion of food from the mouth into the stomach, swallowing also serves as a protective reflex for the upper respiratory tract, preventing unwanted particles from entering the tract. For instance, dysphagia after a stroke can be a devastating problem, as it carries a six fold increased risk of aspiration pneumonia.
In the past, a number of separate treatments have been utilised to assist patients in regaining adequate swallowing reflexes.
For instance, some patients have undergone thermal stimulation treatment. In thermal stimulation treatment, the tonsillar fossa is stimulated by a cooled mirror or probe, and the patient closes his mouth and attempts to swallow.
Alternatively, international patent application no. PCT/US96/17015 describes a method for treating dysphagia with electrical stimulation. The application describes a non-invasive method for treating dysphagia and artificially promoting swallowing by electrical stimulus. A plurality of electrodes are selectively placed in electrical contact with skin over the neck, around the pharyngeal region of the patient, and a series of electrical pulses applied to the electrodes. The electrical pulses selectively stimulate muscle located proximate to the electrodes, to beneficially alter swallowing function. The patent application describes how patients treated by electrical stimulation recovered the ability to swallow at a faster rate than those patients treated by thermal stimulation.